In the use of airborne navigational systems to indicate to aircraft personnel, their own position with respect to the ground, errors inherent in the sensors of the navigational system and the computations must be taken into account.
Thus, navigational sensors which are self-contained and independent of linkages or communication with ground personnel or installations, provide data which has predetermined uncertainty associated with it. In processing the data obtained from the navigational sensors, further uncertainty in the results may be introduced, by the subsequent computation for the position of the airborne vehicle. The computation, for example, may involve various assumptions, for the purpose of simplifying the computations to obtain the aircraft position from the data supplied by the sensors. Additional computational error may be introduced, if the computation is carried out by, for example, an analog computer. Depending on the number of decimal places or significant figures used in the computation, errors may be incurred even if the computation is performed by a digital computer. The sensors used for deriving the position of the aircraft may be in the form of, for example, inertial, stellar, doppler, radar, and systems which measure wind speed and air speed, or combinations thereof. In the use of such navigational sensing arrangements, dead-reckoning procedures are required and the resultant positional information has inherent error or uncertainty associated with it, in view of the errors or uncertainties prevailing with respect to the sensors and the dead-reckoning procedures.
Accordingly, it is an object of the present invention to provide a navigational error correcting system, which corrects the position of an aircraft, derived from an airborne navigational system.
Another object of the present invention is to provide a navigational error correcting system for use in conjunction with multiple aircraft, without requiring that each aircraft be addressed individually.
A further object of the present invention is to provide a navigational error correcting system of the foregoing character, which operates in conjunction with a ground-based installation for determining the position of an individual aircraft.
A still further object of the present invention is to provide a navigational error correcting system, as described, which is highly reliable in operation, and which is secured for use in defense applications as well as for peacetime use.